Welding and plasma arc torches are widely used in the welding, cutting and marking of materials. A plasma torch generally includes an electrode and a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, passages for arc control fluids (e.g., plasma gas), and a power supply. Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and nozzle. The torch produces a plasma arc, a constricted ionized jet of a gas with high temperature and high momentum. Gases used in the torch can be non-reactive (e.g., argon or nitrogen) or reactive (e.g., oxygen or air). In operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). Generation of the pilot arc can be by means of a high frequency, high voltage signal coupled to a DC power supply and the torch or any of a variety of contact starting methods.
During operation of the torch, certain consumable parts become worn and have to be replaced. A known problem in the art is increasing the lifespan of consumables. Specifically, these consumables include torch electrodes, nozzles, and shields. Previous patents assigned to Hypertherm, Inc. of Hanover, N.H. teach techniques for prolonging the lifespan of some of these consumables. For example, U.S. Pat. No. 5,317,126, the contents of which are incorporated herein by reference in their entirety, teaches that the life of a nozzle and an electrode can be extended by providing a plasma bypass channel to increase the mass flow rate of the plasma gas through the plasma chamber. U.S. Pat. No. 5,166,494, the contents of which are incorporated herein by reference, describes altering the flow of plasma gas in conjunction with the transfer of the current flow from the nozzle to the workpiece, and U.S. Pat. No. 5,170,033, the contents of which are incorporated herein by reference in their entirety, teaches that a chamber in the swirl ring can be created and sized to favorably affect the dynamic flow characteristics of the flowing gas when torch operating conditions are changed.
Another known problem in the art of gas-cooled plasma arc cutting torches is increasing the line of site from an operator to a workpiece, particularly along the torch head. A limitation to the sharpness of the torch head is the need to include various design parameters and electrical circuitry therein.